net/strparser/strparser.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Stream Parser
   4  *
   5  * Copyright (c) 2016 Tom Herbert <tom@herbertland.com>
   6  */
   7
   8 #include <linux/bpf.h>
   9 #include <linux/errno.h>
  10 #include <linux/errqueue.h>
  11 #include <linux/file.h>
  12 #include <linux/in.h>
  13 #include <linux/kernel.h>
  14 #include <linux/export.h>
  15 #include <linux/init.h>
  16 #include <linux/net.h>
  17 #include <linux/netdevice.h>
  18 #include <linux/poll.h>
  19 #include <linux/rculist.h>
  20 #include <linux/skbuff.h>
  21 #include <linux/socket.h>
  22 #include <linux/uaccess.h>
  23 #include <linux/workqueue.h>
  24 #include <net/strparser.h>
  25 #include <net/netns/generic.h>
  26 #include <net/sock.h>
  27
  28 static struct workqueue_struct *strp_wq;
  29
  30 static inline struct _strp_msg *_strp_msg(struct sk_buff *skb)
  31 {
  32         return (struct _strp_msg *)((void *)skb->cb +
  33                 offsetof(struct sk_skb_cb, strp));
  34 }
  35
  36 /* Lower lock held */
  37 static void strp_abort_strp(struct strparser *strp, int err)
  38 {
  39         /* Unrecoverable error in receive */
  40
  41         cancel_delayed_work(&strp->msg_timer_work);
  42
  43         if (strp->stopped)
  44                 return;
  45
  46         strp->stopped = 1;
  47
  48         if (strp->sk) {
  49                 struct sock *sk = strp->sk;
  50
  51                 /* Report an error on the lower socket */
  52                 sk->sk_err = -err;
  53                 sk_error_report(sk);
  54         }
  55 }
  56
  57 static void strp_start_timer(struct strparser *strp, long timeo)
  58 {
  59         if (timeo && timeo != LONG_MAX)
  60                 mod_delayed_work(strp_wq, &strp->msg_timer_work, timeo);
  61 }
  62
  63 /* Lower lock held */
  64 static void strp_parser_err(struct strparser *strp, int err,
  65                             read_descriptor_t *desc)
  66 {
  67         desc->error = err;
  68         kfree_skb(strp->skb_head);
  69         strp->skb_head = NULL;
  70         strp->cb.abort_parser(strp, err);
  71 }
  72
  73 static inline int strp_peek_len(struct strparser *strp)
  74 {
  75         if (strp->sk) {
  76                 struct socket *sock = strp->sk->sk_socket;
  77
  78                 return sock->ops->peek_len(sock);
  79         }
  80
  81         /* If we don't have an associated socket there's nothing to peek.
  82          * Return int max to avoid stopping the strparser.
  83          */
  84
  85         return INT_MAX;
  86 }
  87
  88 /* Lower socket lock held */
  89 static int __strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
  90                        unsigned int orig_offset, size_t orig_len,
  91                        size_t max_msg_size, long timeo)
  92 {
  93         struct strparser *strp = (struct strparser *)desc->arg.data;
  94         struct _strp_msg *stm;
  95         struct sk_buff *head, *skb;
  96         size_t eaten = 0, cand_len;
  97         ssize_t extra;
  98         int err;
  99         bool cloned_orig = false;
 100
 101         if (strp->paused)
 102                 return 0;
 103
 104         head = strp->skb_head;
 105         if (head) {
 106                 /* Message already in progress */
 107                 if (unlikely(orig_offset)) {
 108                         /* Getting data with a non-zero offset when a message is
 109                          * in progress is not expected. If it does happen, we
 110                          * need to clone and pull since we can't deal with
 111                          * offsets in the skbs for a message expect in the head.
 112                          */
 113                         orig_skb = skb_clone(orig_skb, GFP_ATOMIC);
 114                         if (!orig_skb) {
 115                                 STRP_STATS_INCR(strp->stats.mem_fail);
 116                                 desc->error = -ENOMEM;
 117                                 return 0;
 118                         }
 119                         if (!pskb_pull(orig_skb, orig_offset)) {
 120                                 STRP_STATS_INCR(strp->stats.mem_fail);
 121                                 kfree_skb(orig_skb);
 122                                 desc->error = -ENOMEM;
 123                                 return 0;
 124                         }
 125                         cloned_orig = true;
 126                         orig_offset = 0;
 127                 }
 128
 129                 if (!strp->skb_nextp) {
 130                         /* We are going to append to the frags_list of head.
 131                          * Need to unshare the frag_list.
 132                          */
 133                         err = skb_unclone(head, GFP_ATOMIC);
 134                         if (err) {
 135                                 STRP_STATS_INCR(strp->stats.mem_fail);
 136                                 desc->error = err;
 137                                 return 0;
 138                         }
 139
 140                         if (unlikely(skb_shinfo(head)->frag_list)) {
 141                                 /* We can't append to an sk_buff that already
 142                                  * has a frag_list. We create a new head, point
 143                                  * the frag_list of that to the old head, and
 144                                  * then are able to use the old head->next for
 145                                  * appending to the message.
 146                                  */
 147                                 if (WARN_ON(head->next)) {
 148                                         desc->error = -EINVAL;
 149                                         return 0;
 150                                 }
 151
 152                                 skb = alloc_skb_for_msg(head);
 153                                 if (!skb) {
 154                                         STRP_STATS_INCR(strp->stats.mem_fail);
 155                                         desc->error = -ENOMEM;
 156                                         return 0;
 157                                 }
 158
 159                                 strp->skb_nextp = &head->next;
 160                                 strp->skb_head = skb;
 161                                 head = skb;
 162                         } else {
 163                                 strp->skb_nextp =
 164                                     &skb_shinfo(head)->frag_list;
 165                         }
 166                 }
 167         }
 168
 169         while (eaten < orig_len) {
 170                 /* Always clone since we will consume something */
 171                 skb = skb_clone(orig_skb, GFP_ATOMIC);
 172                 if (!skb) {
 173                         STRP_STATS_INCR(strp->stats.mem_fail);
 174                         desc->error = -ENOMEM;
 175                         break;
 176                 }
 177
 178                 cand_len = orig_len - eaten;
 179
 180                 head = strp->skb_head;
 181                 if (!head) {
 182                         head = skb;
 183                         strp->skb_head = head;
 184                         /* Will set skb_nextp on next packet if needed */
 185                         strp->skb_nextp = NULL;
 186                         stm = _strp_msg(head);
 187                         memset(stm, 0, sizeof(*stm));
 188                         stm->strp.offset = orig_offset + eaten;
 189                 } else {
 190                         /* Unclone if we are appending to an skb that we
 191                          * already share a frag_list with.
 192                          */
 193                         if (skb_has_frag_list(skb)) {
 194                                 err = skb_unclone(skb, GFP_ATOMIC);
 195                                 if (err) {
 196                                         STRP_STATS_INCR(strp->stats.mem_fail);
 197                                         desc->error = err;
 198                                         break;
 199                                 }
 200                         }
 201
 202                         stm = _strp_msg(head);
 203                         *strp->skb_nextp = skb;
 204                         strp->skb_nextp = &skb->next;
 205                         head->data_len += skb->len;
 206                         head->len += skb->len;
 207                         head->truesize += skb->truesize;
 208                 }
 209
 210                 if (!stm->strp.full_len) {
 211                         ssize_t len;
 212
 213                         len = (*strp->cb.parse_msg)(strp, head);
 214
 215                         if (!len) {
 216                                 /* Need more header to determine length */
 217                                 if (!stm->accum_len) {
 218                                         /* Start RX timer for new message */
 219                                         strp_start_timer(strp, timeo);
 220                                 }
 221                                 stm->accum_len += cand_len;
 222                                 eaten += cand_len;
 223                                 STRP_STATS_INCR(strp->stats.need_more_hdr);
 224                                 WARN_ON(eaten != orig_len);
 225                                 break;
 226                         } else if (len < 0) {
 227                                 if (len == -ESTRPIPE && stm->accum_len) {
 228                                         len = -ENODATA;
 229                                         strp->unrecov_intr = 1;
 230                                 } else {
 231                                         strp->interrupted = 1;
 232                                 }
 233                                 strp_parser_err(strp, len, desc);
 234                                 break;
 235                         } else if (len > max_msg_size) {
 236                                 /* Message length exceeds maximum allowed */
 237                                 STRP_STATS_INCR(strp->stats.msg_too_big);
 238                                 strp_parser_err(strp, -EMSGSIZE, desc);
 239                                 break;
 240                         } else if (len <= (ssize_t)head->len -
 241                                           skb->len - stm->strp.offset) {
 242                                 /* Length must be into new skb (and also
 243                                  * greater than zero)
 244                                  */
 245                                 STRP_STATS_INCR(strp->stats.bad_hdr_len);
 246                                 strp_parser_err(strp, -EPROTO, desc);
 247                                 break;
 248                         }
 249
 250                         stm->strp.full_len = len;
 251                 }
 252
 253                 extra = (ssize_t)(stm->accum_len + cand_len) -
 254                         stm->strp.full_len;
 255
 256                 if (extra < 0) {
 257                         /* Message not complete yet. */
 258                         if (stm->strp.full_len - stm->accum_len >
 259                             strp_peek_len(strp)) {
 260                                 /* Don't have the whole message in the socket
 261                                  * buffer. Set strp->need_bytes to wait for
 262                                  * the rest of the message. Also, set "early
 263                                  * eaten" since we've already buffered the skb
 264                                  * but don't consume yet per strp_read_sock.
 265                                  */
 266
 267                                 if (!stm->accum_len) {
 268                                         /* Start RX timer for new message */
 269                                         strp_start_timer(strp, timeo);
 270                                 }
 271
 272                                 stm->accum_len += cand_len;
 273                                 eaten += cand_len;
 274                                 strp->need_bytes = stm->strp.full_len -
 275                                                        stm->accum_len;
 276                                 STRP_STATS_ADD(strp->stats.bytes, cand_len);
 277                                 desc->count = 0; /* Stop reading socket */
 278                                 break;
 279                         }
 280                         stm->accum_len += cand_len;
 281                         eaten += cand_len;
 282                         WARN_ON(eaten != orig_len);
 283                         break;
 284                 }
 285
 286                 /* Positive extra indicates more bytes than needed for the
 287                  * message
 288                  */
 289
 290                 WARN_ON(extra > cand_len);
 291
 292                 eaten += (cand_len - extra);
 293
 294                 /* Hurray, we have a new message! */
 295                 cancel_delayed_work(&strp->msg_timer_work);
 296                 strp->skb_head = NULL;
 297                 strp->need_bytes = 0;
 298                 STRP_STATS_INCR(strp->stats.msgs);
 299
 300                 /* Give skb to upper layer */
 301                 strp->cb.rcv_msg(strp, head);
 302
 303                 if (unlikely(strp->paused)) {
 304                         /* Upper layer paused strp */
 305                         break;
 306                 }
 307         }
 308
 309         if (cloned_orig)
 310                 kfree_skb(orig_skb);
 311
 312         STRP_STATS_ADD(strp->stats.bytes, eaten);
 313
 314         return eaten;
 315 }
 316
 317 int strp_process(struct strparser *strp, struct sk_buff *orig_skb,
 318                  unsigned int orig_offset, size_t orig_len,
 319                  size_t max_msg_size, long timeo)
 320 {
 321         read_descriptor_t desc; /* Dummy arg to strp_recv */
 322
 323         desc.arg.data = strp;
 324
 325         return __strp_recv(&desc, orig_skb, orig_offset, orig_len,
 326                            max_msg_size, timeo);
 327 }
 328 EXPORT_SYMBOL_GPL(strp_process);
 329
 330 static int strp_recv(read_descriptor_t *desc, struct sk_buff *orig_skb,
 331                      unsigned int orig_offset, size_t orig_len)
 332 {
 333         struct strparser *strp = (struct strparser *)desc->arg.data;
 334
 335         return __strp_recv(desc, orig_skb, orig_offset, orig_len,
 336                            strp->sk->sk_rcvbuf, strp->sk->sk_rcvtimeo);
 337 }
 338
 339 static int default_read_sock_done(struct strparser *strp, int err)
 340 {
 341         return err;
 342 }
 343
 344 /* Called with lock held on lower socket */
 345 static int strp_read_sock(struct strparser *strp)
 346 {
 347         struct socket *sock = strp->sk->sk_socket;
 348         read_descriptor_t desc;
 349
 350         if (unlikely(!sock || !sock->ops || !sock->ops->read_sock))
 351                 return -EBUSY;
 352
 353         desc.arg.data = strp;
 354         desc.error = 0;
 355         desc.count = 1; /* give more than one skb per call */
 356
 357         /* sk should be locked here, so okay to do read_sock */
 358         sock->ops->read_sock(strp->sk, &desc, strp_recv);
 359
 360         desc.error = strp->cb.read_sock_done(strp, desc.error);
 361
 362         return desc.error;
 363 }
 364
 365 /* Lower sock lock held */
 366 void strp_data_ready(struct strparser *strp)
 367 {
 368         if (unlikely(strp->stopped) || strp->paused)
 369                 return;
 370
 371         /* This check is needed to synchronize with do_strp_work.
 372          * do_strp_work acquires a process lock (lock_sock) whereas
 373          * the lock held here is bh_lock_sock. The two locks can be
 374          * held by different threads at the same time, but bh_lock_sock
 375          * allows a thread in BH context to safely check if the process
 376          * lock is held. In this case, if the lock is held, queue work.
 377          */
 378         if (sock_owned_by_user_nocheck(strp->sk)) {
 379                 queue_work(strp_wq, &strp->work);
 380                 return;
 381         }
 382
 383         if (strp->need_bytes) {
 384                 if (strp_peek_len(strp) < strp->need_bytes)
 385                         return;
 386         }
 387
 388         if (strp_read_sock(strp) == -ENOMEM)
 389                 queue_work(strp_wq, &strp->work);
 390 }
 391 EXPORT_SYMBOL_GPL(strp_data_ready);
 392
 393 static void do_strp_work(struct strparser *strp)
 394 {
 395         /* We need the read lock to synchronize with strp_data_ready. We
 396          * need the socket lock for calling strp_read_sock.
 397          */
 398         strp->cb.lock(strp);
 399
 400         if (unlikely(strp->stopped))
 401                 goto out;
 402
 403         if (strp->paused)
 404                 goto out;
 405
 406         if (strp_read_sock(strp) == -ENOMEM)
 407                 queue_work(strp_wq, &strp->work);
 408
 409 out:
 410         strp->cb.unlock(strp);
 411 }
 412
 413 static void strp_work(struct work_struct *w)
 414 {
 415         do_strp_work(container_of(w, struct strparser, work));
 416 }
 417
 418 static void strp_msg_timeout(struct work_struct *w)
 419 {
 420         struct strparser *strp = container_of(w, struct strparser,
 421                                               msg_timer_work.work);
 422
 423         /* Message assembly timed out */
 424         STRP_STATS_INCR(strp->stats.msg_timeouts);
 425         strp->cb.lock(strp);
 426         strp->cb.abort_parser(strp, -ETIMEDOUT);
 427         strp->cb.unlock(strp);
 428 }
 429
 430 static void strp_sock_lock(struct strparser *strp)
 431 {
 432         lock_sock(strp->sk);
 433 }
 434
 435 static void strp_sock_unlock(struct strparser *strp)
 436 {
 437         release_sock(strp->sk);
 438 }
 439
 440 int strp_init(struct strparser *strp, struct sock *sk,
 441               const struct strp_callbacks *cb)
 442 {
 443
 444         if (!cb || !cb->rcv_msg || !cb->parse_msg)
 445                 return -EINVAL;
 446
 447         /* The sk (sock) arg determines the mode of the stream parser.
 448          *
 449          * If the sock is set then the strparser is in receive callback mode.
 450          * The upper layer calls strp_data_ready to kick receive processing
 451          * and strparser calls the read_sock function on the socket to
 452          * get packets.
 453          *
 454          * If the sock is not set then the strparser is in general mode.
 455          * The upper layer calls strp_process for each skb to be parsed.
 456          */
 457
 458         if (!sk) {
 459                 if (!cb->lock || !cb->unlock)
 460                         return -EINVAL;
 461         }
 462
 463         memset(strp, 0, sizeof(*strp));
 464
 465         strp->sk = sk;
 466
 467         strp->cb.lock = cb->lock ? : strp_sock_lock;
 468         strp->cb.unlock = cb->unlock ? : strp_sock_unlock;
 469         strp->cb.rcv_msg = cb->rcv_msg;
 470         strp->cb.parse_msg = cb->parse_msg;
 471         strp->cb.read_sock_done = cb->read_sock_done ? : default_read_sock_done;
 472         strp->cb.abort_parser = cb->abort_parser ? : strp_abort_strp;
 473
 474         INIT_DELAYED_WORK(&strp->msg_timer_work, strp_msg_timeout);
 475         INIT_WORK(&strp->work, strp_work);
 476
 477         return 0;
 478 }
 479 EXPORT_SYMBOL_GPL(strp_init);
 480
 481 /* Sock process lock held (lock_sock) */
 482 void __strp_unpause(struct strparser *strp)
 483 {
 484         strp->paused = 0;
 485
 486         if (strp->need_bytes) {
 487                 if (strp_peek_len(strp) < strp->need_bytes)
 488                         return;
 489         }
 490         strp_read_sock(strp);
 491 }
 492 EXPORT_SYMBOL_GPL(__strp_unpause);
 493
 494 void strp_unpause(struct strparser *strp)
 495 {
 496         strp->paused = 0;
 497
 498         /* Sync setting paused with RX work */
 499         smp_mb();
 500
 501         queue_work(strp_wq, &strp->work);
 502 }
 503 EXPORT_SYMBOL_GPL(strp_unpause);
 504
 505 /* strp must already be stopped so that strp_recv will no longer be called.
 506  * Note that strp_done is not called with the lower socket held.
 507  */
 508 void strp_done(struct strparser *strp)
 509 {
 510         WARN_ON(!strp->stopped);
 511
 512         cancel_delayed_work_sync(&strp->msg_timer_work);
 513         cancel_work_sync(&strp->work);
 514
 515         if (strp->skb_head) {
 516                 kfree_skb(strp->skb_head);
 517                 strp->skb_head = NULL;
 518         }
 519 }
 520 EXPORT_SYMBOL_GPL(strp_done);
 521
 522 void strp_stop(struct strparser *strp)
 523 {
 524         strp->stopped = 1;
 525 }
 526 EXPORT_SYMBOL_GPL(strp_stop);
 527
 528 void strp_check_rcv(struct strparser *strp)
 529 {
 530         queue_work(strp_wq, &strp->work);
 531 }
 532 EXPORT_SYMBOL_GPL(strp_check_rcv);
 533
 534 static int __init strp_dev_init(void)
 535 {
 536         BUILD_BUG_ON(sizeof(struct sk_skb_cb) >
 537                      sizeof_field(struct sk_buff, cb));
 538
 539         strp_wq = create_singlethread_workqueue("kstrp");
 540         if (unlikely(!strp_wq))
 541                 return -ENOMEM;
 542
 543         return 0;
 544 }
 545 device_initcall(strp_dev_init);